Chuck for frazing machines



Sept. 1 4 Y E. E CALHOUN 2,38

' Caucx FOR FRAZING MACHINES Filed July '7, 1943 4.; ATTOR-NEY',

Patented Sept. 25, 1945 7 Earl E.

Calhoun, Shulls Mills, N.- 0., 'assignor to David P. Lavietes, Boone, N.C.-

Application July 7, 1943, Serial No. 493,732

i i I 11 Claims.

The invention relates to chucks for frazing mawork block and the millingtool in accordance with the contour of said pattern or model.

In the manufacture of smokers pipes, the frazing of a block of briar orother wood is the second step in the manufacture of. smokers pipes aftera block has been roughlycut to 'a sizeand shape suitable for producing apipe of the desired design. The shape of the block bears no resemblanceto the bowl and stem of'a finished. pipe and much of: the Wood of theblock must be removed by the milling tool to reduce the block to thedesired contour and to dimensions permitting the finishing operationsupon therough finished pipe or stum'mel by suitable abrading tools.

I In the manufacture of pipes from briar or other hard woods, the firstmanufacturing step is to bore out a portion of the wood block to formthe bowl of the pipe. Usually the portion of the wood about the outertop of the bowl is turned and the .top face of the bowl trued up. Thisis done with a single tool and is necessary to permit the engagement andproper positioning of the block by the chuck of a frazing machine.

a Great difiiculty has been experienced in properly holding a block in achuck in a, manner to avoid its being displaced in relation to thepattern or model by the stresses from the'milling tool with a resultantwastage of time and materi'alndue to improper action of the tool. The

block must be accurately positioned and located in its relation to thepattern-or model and any shifting of the block by the very considerablestresses thereon from the milling tool williresult in a stummel in whichthe stem of the pipe and the bowl. will not be in proper. alinement andthe bore of; the latter will be off center.

In a chuck as ordinarily used in frazing machines before my invention,the clutch jaws were manually actuated by a tapered stem having a screwthreaded shank mounted in the jaw carryingblockacting uponthejaws andprovided with ualwingghead. With this arrangement the fingers f'anoperator were used for turning the screw to set or to release thejaws and the gripping action of the jaws was determined by the strengthof the operators fingers and varied with vdifierent operators and withdifferent operations. Furthermore the point of application of pressureto the jaws bysaid stem was remote from the point of their bite upon thewood of the block and there wasnot only excessivewear on the partsultimately resulting in lost motion tending towards slippage or shiftingof the block but increased difficulty ingetting a proper contact betweenthe jaws and the block. At times a hand wrench was used to develop thenecessary gripping action of the jaws. A further difficulty was thepossible splitting or breakage'of the wood block because of-anuncontrolled pressure upon the block by the jaws, particularly if, as aresult of frazing, a thin wall for the bowl is formed.

, With chucks of the-type heretofore used, an operator not only wasrequired to stand at all times'while operating the machine but was inalmost constant movement between the actuating member of the pattern ormodel carrier and the chuck, since the actual time interval required infrazing a pipe bowl and stem is very short.

' In the chuck of my inventiona uniform predetermined pressure by thegripper jaws is developed ,with operation of the machine upon succeedingblocks. The chuck not only may be adjusted to adapt it to pipes havingbowls of different diameters but to nicely regulate the gripper movementto ensure the development of pressure by the jaws sufficient to preventany possible looseness of the block resulting in its shifting inrelation on either the jaws or the actuating wedge, this may be taken upby adjustment of the wedge in relation to the jaws. q

Actuation of the jaws is by means of a short lever, the power of whichis compounded not only by the wedge but by that of an intermediatemechanism.

Locating the wedge adjacent and beyond the ends of the jaws facilitatesthe centering of the bore of the bowl in relation to the jaws and thetruing up of the block in relation to the jaw head, and permit the wedgeto actas an ejector pin when releasing the jaws by movement of theactuating lever.

A spring acts upon the jaw actuating mechanisms to facilitate the leveraction in releasing the jaws and to prevent accidental movement of thejaws before a block is mounted in the chuck.

The wedge pin is so formed as to prevent accidental movement of the jawswhen the wedge is disengaged therefrom.

The operator of a frazing machine having a chuckv embodying theinvention, after the ma chine hasbeen adjusted to produce stummels for apipe of a particular design, need not move from end to end of themachineand is relieved from leg and finger strains resulting from the operationof the type of frazing machines commonly in use prior to my invention.

The invention consists primarily in achuck for use me frazing machine ofa type having a milling tool, a movable frame capable of lineal androtary movement in relation to said tool, a pattern shaft rotatablymounted in said frame and a guide adapted to cooperate with a pattern onsaid shaft and control movements of said frame inaccordance with saidpattern; said chuck embodying therein a frame, a base supported thereby,a plurality of jaws pivotally mounted in andprbjectingfrom said-base, apin passing through said baseand between said jaws having a wedgeshapedhead extending beyond the free ends of said'jaws whereby withmovemerit-of said head towards and within said jaws, outward pressure isdeveloped adjacent the free ends of said jaws, lever actuated means forimparting axial movement to said pinto move said headt'owards said jaws,and means acting independently of said lever actuated means forimparting a reverse -movement to said pin to contract said jaws andeject work. therefrom; and

in such other novel features of construction and combination of partsasare hereinafter set forth and described and more particularly pointout ihthe claims; hereto appended;

Referring to the drawing,

Fig. 1 is a front view, shown more or less conventionally, bf a; frazingmachine supplied with achuck embodying my invention;

Fig. 2 is a side View, partly broken away, of a chuck remove rrdm themachine;

Fig. 3 is a plan View of Fig. 2;

Fig. 4 is a view of the wedge .pin;

Fig. 5 is a perspectivevi'ew of one of the gripper jaws;and T Fig. 6 isa perspective view of 'awooden block prepared for frazing.

Like numerals refer to like: parts throughout the several views.

1 In the accompanying drawing, I have illustrated achuck embodying myinvention as applied to a type of frazin machine well known in thepipemanufacturing-industry. This machine has a milling tool IO -and apattern frame I l slidably and pivotally mounted onaguide bar 12 so asto be capable ofsimul'taneous lineal and oscillatory movementinrel'ation to said tool. Mounted in said frame H is a shaft, l3rotatable'by means of a hand wheel [4. In the length of this shaft is apattern or model I5 adapted for engagement with a fixed guide orreaction member 16 which permits movement of the pattern or modelcarrying frame toward and from the milling tool only in accordance withthe said pattern or model. The machine may be adjusted in variousrespects to adapt it for use with differ ent patterns or models. Thisisimmaterial to the presentinvention.

One end of the shaft 13 has an axial socket by means of which a chuck ismounted upon said shaft so as to be movable therewith.

Referring more particularly to a chuck embodying my invention, itconsists of a block I! having a stem I8 by which it is rigidly mountedon the shaft [3. Adjustably mounted on said block, is a frame l9supporting a base carrying the gripper jaws 20. Said jaws are pivotedadjacent one end thereof in a base 2| having a finished, plane faceabout the jaws.

Passing through a space within the jaws 20; is

a round pin 22 havin an enlarged circular head 25' positioned beyond theends of the jaws." The edge of this head is bevelled inwardly towardsthe axis of the jaw structure as shown at 24 so that with movement ofthe head23 towards and within the ends. of the jaws a strong wedgingaction occurs causing expansion of the jaw structure. The pin 22 istapered towards. the head 23 for a distance approximating the length ofthe jaws affording a portion at the erid icifsaid tapered portionadjacent the heels of the jaws of dimensions so that withmovement of thepin to move its head away from the jaws, engagement of this portion withsaid. heels will contract the jaw. structure.

As illustrated in Fig.5, each jaw comprises a gripper arm 25 and a.heel. 26. adjacent which the jaw is pivoted.- upon the base 2.l-.Thisbas'e also carriesfa plurality of fixed. separators 2]. The inner,wall of each arm. 25. is con'cavely curved to afford clearance forthewedge pin 22. The inner faces ,of' the heels are spaced. apartsufiiciently to permit free oscillationof the jaws whenthe taperedportion of the pin 22.:is adjacent said heels, but. cause engagement of,said heels with the portion of said pin;adjacent an end.of said taperedportion. The outer face of. each arm 25 adjacentits freeend may be.roughened to iioncrliiase the bite of the jaw. upon. the wooden loc. Theend efthe'v pin;2,2 remote from. the'head 23 is exteriorlyscrewthreadedas at 28 and this end portion passes throughahole in thebase 2| and the frame l9 andisadjustably mountedby meansof screwthreadsin a bearing stud 29: A set screw 30; is usedto lockthe pin 22inany adjusted position. Intermediate. the stud, 29 and the frame 19 is achannelledfittingtl carrying a replaceable, slightly compressiblepad 32against which an actuating. cam-J forv imparting axial movement to thepin 22'bears.

A bifurcated actuating camframe 33;;has;its arms mounted uponopposite-ends of the stud 29. It will be noted that except for thebearing pad 32, the actuating' mechanism for the wedge pin, is carriedin its entirety. by. sai'dipin andtis unconnected with'otherparts of thechuck excepting therethrough. As will hereinafter. appear, thisconstruction permitsregulati'on of tlie-jaw actionto adapt. thechuektobowlbores 'o'ffdifferent diameters, and also tocontroltheipressure exerted. upon :said jaws by.the .powerful actuatingmechanism for the jaws acting through the wedge Pin head23.

1 'Actingupon the pin 22 through the stud 29 is a helical spring 34 thecoil of which is positioned upon a pin 35 carried by the frame [9, oneprojecting end of this spring bearing upon the stud 29 and the otherprojecting end, upon the block I l. -;.The actuating cam frame 33 has alever handle 36. so'formed as to have its movementwhen setting the jawsstopped by engagement with some .part of the machine adjacent the end ofthe shaft [3. The cam frame may have flattened portions upon oppositeends of each cam surface thereon to ensure locking of the frameimmediatelyfollowing disengagement of said cam surfaces from the seat32.

- The wooden block for forming the stummel is shown in- Fig. 6, the boreof the bowl being located atp3 l,and the finished outer surface aboutthe .top of the bowl at 38. The portion of the block from which the pipestem is formed is shown at 39.

The operation of a frazing machine fitted with a chuck embodying theinvention, is substantially chuck in mounting and discharging the work,

may beseated upon a stool with said wheel within convenient reach of hisright hand and the chuck and containers for the wooden blocks and thefinished stummels within convenient reach of his left hand. I 1 Afterthe frazing machine and the chuck have been properly adjusted, theoperator merely moves the lever 36 away from the stern l8, thus turningthe cam frame 33 about the stud 29. This movement of the cam frameimparts lineal movement to the pin 22 to an extent to disengage its head23 from the free ends of the jaws and engages the portion of the pinadjacent the large end of the taper of said pin with the heels of theseveral jaws. This movement of the pin which is by action of the spring34 upon the stud 29, closes or contracts the jaws. The taper of the pin22 is of a'length to ensure a proper timing inthe action of the taperedportion of said pin and of the head 23.

' The bore of the part 36 of the wooden block is then slipped over theclosed or contracted jaws 'until its faced top abuts against and isflush with 'the plane face of the base 2|.

Whatever the adjustment of the chuck may be, the block always "has afree sliding movement in relation to the controlling movement of theframe I3 during the frazing operation.

The operator, using his right hand, then moves the lever 36 towards thestem l8 until further movement thereof is positively stopped. Thismovement of the lever turnsthe cam frame about the stud-29, the camsurfaces on said frame imparting lineal movement to the pin 22 throughthe movement of said stud. By using a slightly "compressible orresilient seat 32, slight flexibility 20 against the wall of the bowl.This movement of the cam frame tensions the spring 34.

This movementof the pin 22 by the cam frame 33 is a short, powerful oneand amounts to merely a fraction of an, inch. During this movement, thehead 23 of the pin approaches and engages the ends of the several jaws20, the bevelled edge of'said head camming the jaws outwardly into theexpanded or open position and into engage-.

ment with the inner wall of the pipe bowl. Prior to or duringthismovement of the jaws, the tapered portion of the pin 22 is so movedas to provide clearance adjacent the heels 26 of the several jaws topermit such jawmovement.

The operator may use the palm of his right hand in actuating the lever36 to expand the jaws.

The jaws having been expanded or engaged within the block in the mannerdescribed, the frazing machine is operated to form the stummel in theusual manner. The operator may remain seated during the mounting,frazing and discharge operations.

Following the completion of the frazing operation, the operator merelymoves the lever 36 away from the stem l8 contracting or closing the jawsso as to disengage them from the bowl and permit it to be dischargedfrom the chuck. During this operation, the pin 22 acts as an ejector,the operator being required merely to catch the discharged stummel inhis left hand and toss it into limit its camming action on said jaws.

a conveniently positionedcontainer.

The bowls of pipes of different designs may have bores of differentdiameters, and since any slippage or shifting of the block in relationto the chuck jaws will result in spoilage and wastage, means foradjusting the gripping action of the chuck jaws is provided to adapt thechuck for use in the production of a wide range of variation in thediameters of the bores in pipes, as well as to control the pressure ofthe jaws against the wall of the bowl at all times.

If the extent of expansion of the jaws is so great as to requireexcessive pressure upon the lever 36 and the power compounding mechanismactuated thereby to expand or set the jaws, said power compoundingmechanism consisting of the cam frame 33 and the cam edge of the head 23of the pin 22, or to prevent a, full movement of the lever 36 to itsstop position, it is merely necessary to release the lock screw 30, andturn the pin 22 in the stud 29 in a direction to move the head 23outwardly of the free ends of the jaws 20 so as to If on the contrary,the jaws are not expanded to an extent to engage the inner wall of thebowl with sufficient pressure to firmly hold the wooden block, after thescrew 30 has been released, the pin 22 is so turned as to advance thehead 23 towards the free ends of the jaws thus increasing its cammingaction to impart greater expansion of the jaws.

Since there is great vibration about a frazing machine, the set screw 30must be set hard against thepin 22 following each adjustment, the screwthreads upon the pin 22 aiding in securing the desired tightness of theset of said screw.

In adjusting the chuck to control pressure by the jaws, a jaw movementof only a thousandth of an inch or so may be required, although whenadjusting to size variation of different bowls, a much greater movement,of the jaws may be necessary.

used prior to the invention.

tifi-of the jaw action irrespective or the amount of turning movement ofthe pin 22 during adjustment'. i I v j The saving of time in mounting a;block-and discharging a completed 'stiiinii'iel by v i in movement ofthe operator about the machine, and theoo nservationof the ener'gy'ofthe Operatoi', materially'ihcreases the output capacity of aHazing-machine havinga chuck embodying the invention, as compared w'iththe operation'of siich a machine having the form of chuck commonly It isnot'my intention tOliinit the invention to the precise details ofconstruction shown in the drawing, it being apparent that such arecapable of wide variation without departing from the spirit and scope ofthe invention.

Having described the invention, what I claim as new and desire to haveprotected by Letters Patent is: j I

1. A chuck for use infr'azing'machines of a type having a milling tool;a'frame capable of lineal and oscillatory movement in relation to saidtool, a pattern shaft rotatably mounted in said frame and a guideadapted to coop'erate with a pattern on said shaft to control movementsof said frame in accordance with said pattern, embodying therein a frameadapted to be mounted on'said pattern shaft, a base supported thereby, aplurality of jaws pivotally mounted on and projecting from said base, apin passing through said base and between said jaws having a wedgeshaped head extending beyond the 7 free ends of said jaws whereby withmovement of 'saidhead towards and within said jaws outward pressure isdeveloped adjacent the free ends of said jaws, a lever actuated meansfor impartingaxial movement to said pin to move said head towards saidjaws, and means acting independently of said lever actuati'ng means forimparting a reverse movement to said pin to contract saidjaws withmovement Of Said'had outwardly thei'eof and ejeCt' Work from the chuck.V

2; A chuck for use frazing machines of a t-ypeh'avi'ng a milling tool, aframe capable of lineal and oscillatory movement in relation to Saidtom; apattern shaft rotatab-ly mounted in said frame anda guideadaptedto cooperate'with a pattern on said-shaft to -control movements of saidframein'acoo'rdancewith said pattern, em-

bodying therein a frame adapted to be mounted on said pattern-shaft, abase supported thereby, a plurality of jaws pivetally mounted on andproj'ecting' from saidbase, apin passing throughsaid base and betweensaid j aws having a wedge shaped head extending beyond the free ends'ofsaid jaws, whereby withmovement of said hea-dtowa'rds and within saidjaws outward pressure is developed adjacent the free ends of said'jaws;a stud, connections between said pin and said stud, a cam framepivotally mounted on said stud, av bearing engageable by the cam surfaceon said cam frame, an actuatinglever on said'cam frame t'om'ove 'saidhead'towards; and'within .said'jaw's, and means acting' independently ersai actuating lever for imparting a reverse movement to said pin tocontract said jaws with movement of said head'outwardly thereof andeject work from the chuck.

L 3 Aflchuck for use in fr'azing machines of a type having a millingtool, a frame capable of 5 lineal andoscillatory movement in relation tosaid tool, a pattern shaft rotatably' mounted in said frame-Land aguideadapted to cooperate with a pattern on said shaft to control movementsof said frame: in: accordance with said pattern, embodying thereinaframe adapted to be mounted on said pattern shaft, a base supportedthereby,. a plurality of jaws pivotally mounted on and projecting from"said base, a pin passing through said-base and between said jaws havinga wedge shaped head extending beyond the free ends of said jaws wherebywith movement or said head towards and within said jaws outward pressureis developed adjacent the free ends ofs'a-id jaws, each-of said jawshaving a heel adjacentits point of'pivotal support and-said pinbeingtapered to- \i/ards-sa'id head and having a portion adjacent theheels of 'saidjaws, of larger dimensionsthan said tapered portion; leveractuated means for imparting axial movement to said pin towardssai'dj'aws and means acting independently of said leveract'uatingmeansfor imparting a reverse movement to said head'out-wardly' thereofand eject work from the chuck.

4 A chuck for use in frazing machines of a ty e having amilling tool, a;frame capable of lineal and oscillatory movement in relation to saidtool; a pattern-shaft i'otatably mounted in said f'raineand a guideadapted to cooperate with a pattern on said shaft to control movementsof saidframe in accordance with said pattern, embodying therein a frameadapted to be mounted on said pattern shaft, a base supported thereby,aplurality of jaws pivotally mounted'on and projecting fromsaidbase,a'pir'i passing through said base and between said jaws having" a wedgeshaped head extending beyond the'free ends of the jaws whereby withmovement of said head towards and within said jaws outward pressureisapli ied adjacent the free ends of said jaws, lever actuated means forimparting" axial moveiirient to'said pin'tomove said head towards saidjaws anda spring acting upon saidpiii independently'of lever actuatedmeans biased'to' move the head'of' sa'id' pin away frd'ni said jaws tocontract saidijaws' and eject work from the chuck} f 5."A chuck for Lisein tracing mahiiies of a type'having'amilling tool, a frame capable oflineaiand oscillatory movment'in relation to said 5 tool, a patternshaft i'otatably mountedin said said whereby with-movement of said headtowards and within said jaws outwardpressure is applied adjacent thefree of saidjaws, means whereby said pin may be axially adjustedposition i of. said head inrelation to 7 .and the movement-bf said jawsto control the pressure exerted" thereby" and to adapt the chuck for usewith openings having different diameters, lever I actuated means forimparting-movement to said pin andjmeans acting independently of saidlever? actuatin means for imparting a reverse movement to said'pintocontract said jaws with movement of said'head outwardly and eject workfrom the chuck.

6. A chuck for usein frazing machines of a type having a milling tool, aframe capable of lineal and oscillatory movement in relation to saidtool, a pattern shaft rotatably mounted in said frame and a guideadapted to cooperate with a pattern on said shaft to control movementsof said frame in accordance with said pattern, embodying therein a frameadapted to be mounted on said pattern shaft, a base supported thereby, aplurality of jaws pivotally mounted on and projecting from said base, around pin passing through said base and between said jaws and having acircular head, the edge of which is bevelled towards the axis of saidpin and extends beyond the free ends of said jaws whereby with movementof said head towards and within said jaws outward pressure is appliedadjacent the free ends of said jaws, means whereby said pin may beaxially adjusted to vary the position of said head in relation to andthe movement of said jaws to control the pressure exerted thereby and toadapt the chuck for use with openings having different diameters, leveractuated means for imparting movement to the said pin and means actingindependently of said lever actuating means for imparting a reversemovement to said pin to contract said jaws with movement of said headoutwardly and eject work from the chuck.

7. A chuck for use in frazing machines of a type having a milling tool,a frame capable of lineal and oscillatory movement in relation to saidtool, a pattern shaft rotatably mounted in said frame and a guideadapted to cooperate with a pattern on said shaft to control movementsof said frame in accordance with said attern, embodying therein a frameadapted to be mounted on said pattern shaft, a basesupported thereby,

' a plurality of jaws pivotally mounted on and projecting from saidbase, a pin passing through said base and between said jaws having awedge shaped head extending beyond the free ends of said jaws wherebywith movement of said head towards and within said jaws outward pressureis developed adjacent the free ends of said jaws, each of said jawshaving a heel adjacent its point of pivotal support and said pin beingtapered towards said head with a portion adjacent the heels of said jawsof larger dimensions than said tapered portion, means whereby said pinmay be axially adjusted to vary the position of said head in relation toand the movement of said jaws to control the pressure exerted therebyand to adapt the chuck for use with openings having different diameters,lever actuated means for imparting movement to said pin towards saidjaws, and means acting independently of said lever actuating means forimparting a reverse movement to said head to contract said jaws withmovement of said head outwardly, and eject Work from the chuck.

8. A chuck for use in 'frazing machines of a type having a milling tool,a frame capable of lineal and oscillatory movement in relation to saidtool, a pattern shaft rotatably mounted in said frame and a guideadapted to cooperate with a pattern on said shaft to control movementsof said frame in accordance with said pattern, em-

' bodying therein a frame adapted to be mounted on said pattern shaft, abase supported thereby, a plurality of jaws pivotally mounted on andprojecting from said base, a pin passing through said base and betweensaid jaws having a wedge shaped head extending beyond the free ends; ofsaid jaws, a stud, connections between said pin and said stud, meanswhereby said pin may be axially adjusted in said stud to vary themovement of said jaws to control the pressure exerted thereby and toadapt the chuck for use with openings having different diameters, andlever actuated means for imparting movement to said pin.

9. A chuck for use in frazing machines of a type having a milling tool,a frame capable of lineal and oscillatory movement in relation to saidtool, a pattern shaft rotatably mounted in said frame and a guideadapted to cooperate with a pattern on said shaft to control movementsof said frame in accordance with said pattern, embodying therein a frameadapted to be mounted on said pattern shaft, a base supported thereby, aplurality of jaws pivotally mounted on and projecting from said base, around pin passing through said base and between said jaws and having acircular head, the edge of which is bevelled towards the axis of saidpin and extends beyond the free ends of said jaws whereby pressure isapplied adjacent the free ends of said jaws, each of said jaws having aheel adjacent its point of pivotal support, said pin being taperedtowards said head and having a portion adjacent the heels of said jawsof larger dimensions than said tapered portion and exterior screwthreads adjacent its end opposite said head, a stud having a screwthreaded opening therein by which said pin is rotatably connected withsaid stud, means locking said pin in relation to said stud, a cam framepivotally mounted on said stud, a bearing cooperating with said camframe and an actuating lever on said cam frame.

10. A chuck for use in frazing machines of a type having a milling tool,a frame capable of lineal and oscillatory movement in relation to saidtool, a pattern shaft rotatably mounted in said frame and a guideadapted to cooperate with a pattern on said shaft to control movementsof said frame in accordance with said pattern, embodying therein a frameadapted to be mounted on said pattern shaft, a base supported thereby, aplurality of jaws pivotally mounted on and projecting from said base, around pin passing through said base and between said jaws and having acircular head, the edge of which is bevelled towards the axis of saidpin and extends beyond the free ends of said jaws whereby pressure isapplied adjacent the free ends of said aws, each of said jaws having aheel adjacent its point of pivotal support, said pin being taperedtowards said head and having a portion adjacent the heels of said jawsof larger dimensions than said tapered portion and exterior screwthreads adjacent its end opposite said head, a stud having a screwthreaded opening therein by which said pin is rotatably connected withsaid stud, means looking said pin in relation to said stud, a cam framepivotally mounted on said stud, a bearing cooperating with said camframe, an actuating lever on said frame and a spring acting upon saidstud and biased to move the head away from said aws. J 11; A chuck foruse in frazing machines of a ty e having a milling tool, a frame capableof 1meal and oscillatory movement in relation to said tool, a patternshaft rotatably mounted in said frame and a guide adapted to cooperatewith a pattern on said shaft to control movements of said frame inaccordance with said pattern, embodying therein a frame adapted to bemounted on said pattern shaft, a base supported thereby, a plurality ofjaws pivotally mounted on and projecting from said base, a round pinpassing through said base and between said jaws and having a circularhead, the edge of which is bevelled towards the axis of said pin andextends beyond the free ends of said jaws whereby pressure is appliedadjacent the free ends of .said jaws, each pivotal support, said pinbeing tapered towards its end opposite said head, a stud having a screwthreaded opening therein by which said pin is rotatably connected withsaid stud, means looking said pin in relation to said stud, a cam framepivotally mounted on said stud, a slightly compressible bearingcooperating with said cam frame of said jaws having a heel adjacent itspoint of 10 and an actuating leverons'aid'cam frame.

EARL E. CALHOUN.

